FK506 enhances fibrogenesis in in vitro and in vivo models of liver fibrosis in rats

Evaluation of Long-Term Outcomes of Direct Acting Antiviral Agents in Chronic Kidney Disease Subjects: A Single Center Cohort Study

BACKGROUND

The chronic kidney disease (CKD) population, including kidney transplant recipients (KTRs) and subjects on renal replacement therapy, is particularly vulnerable to unfavorable outcomes from chronic hepatitis C (CHC). Currently, there are oral direct-acting antiviral agents (DAAs) available to eradicate the virus with favorable short-term outcomes; however, their long-term effects are lacking. The aim of the study is to assess the long-term efficacy and safety of DAA therapy in the CKD population.

METHODS

An observational, cohort single-center study was performed. Fifty-nine CHC subjects with CKD, treated with DAAs between 2016 and 2018, were enrolled in the study. Safety and efficacy profiles were assessed, including sustained virologic response (SVR), occult hepatitis C infection (OCI) incidence, and liver fibrosis.

RESULTS

SVR was achieved in 96% of cases (n = 57). OCI was diagnosed only in one subject following SVR. Significant liver stiffness regression was observed 4 years after SVR compared to baseline values (Mdn = 6.1 kPa, IQR = 3.75 kPa; 4.9 kPa, IQR = 2.9 kPa), p < 0.001. The most common adverse events were anemia, weakness, and urinary tract infection.

CONCLUSION

DAAs provide a safe and effective cure for CHC in both CKD patients and KTRs with a favorable safety profile in the long-term follow-up.

Host and immunosuppression-related factors influencing fibrosis occurrence post liver transplantation

Post liver transplantation (LT) fibrosis has a negative impact on graft function. Cytokine production in the host immune response after LT may contribute to the variable CYP3A-dependent immunosuppressive drug disposition, with subsequent impact on liver fibrogenesis, together with host-related factors. We aimed to investigate whether the cytochrome P4503A5*3 (CYP3A5*3) or TBX21 genotypes impact post-LT liver fibrogenesis. Furthermore, the impact of immunosuppressants on cellular apoptosis has been evaluated using human hepatocytes harvested from cirrhotic explanted livers. We have enrolled 98 LT recipients that were followed for occurrence of liver fibrosis for at least 12 months. There was a statistically significant higher trough level of TAC in patients with homozygous CC-TBX21 genotype (7.83 ± 2.84 ng/ml) vs. 5.66 ± 2.16 ng/ml in patients without this genotype (p = 0.009). The following variables were identified as risk factors for fibrosis ≥2: donor age (p = 0.02), neutrophil to lymphocyte ratio (p = 0.04) and TBX21 genotype CC (p = 0.009). In the cell culture model cytometry analysis has indicated the lowest apoptotic cells percentage in human cirrhotic hepatocytes cultures treated with mycophenolate mofetil (MMF) (5%) and TAC + MMF (2%) whereas the highest apoptosis percentage was registered for the TAC alone (11%). The gene expression results are concordant to cytometry study results, indicating the lowest apoptotic effect for MMF and MMF + TAC immunosuppressive regimens. The allele 1993C of the SNP rs4794067 may predispose to the development of late significant fibrosis of the liver graft. MMF-based regimens have a favourable anti-apoptotic profile in vitro, supporting its use in case of LT recipients at high risk for liver graft fibrosis.

Intestinal stenosis in Crohn's disease shows a generalized upregulation of genes involved in collagen metabolism and recognition that could serve as novel anti-fibrotic drug targets

BACKGROUND AND AIMS

Crohn's disease (CD) can be complicated by intestinal fibrosis. Pharmacological therapies against intestinal fibrosis are not available. The aim of this study was to determine whether pathways involved in collagen metabolism are upregulated in intestinal fibrosis, and to discuss which drugs might be suitable to inhibit excessive extracellular matrix formation targeting these pathways.

METHODS

Human fibrotic and non-fibrotic terminal ileum was obtained from patients with CD undergoing ileocecal resection due to stenosis. Genes involved in collagen metabolism were analyzed using a microfluidic low-density TaqMan array. A literature search was performed to find potential anti-fibrotic drugs that target proteins/enzymes involved in collagen synthesis, its degradation and its recognition.

RESULTS

mRNA expression of collagen type I (COL1A1, 0.76 ± 0.28 versus 37.82 ± 49.85, p = 0.02) and III (COL3A1, 2.01 ± 2.61 versus 68.65 ± 84.07, p = 0.02) was increased in fibrotic CD compared with non-fibrotic CD. mRNA expression of proteins involved in both intra- and extracellular post-translational modification of collagens (prolyl- and lysyl hydroxylases, lysyl oxidases, chaperones), collagen-degrading enzymes (MMPs and cathepsin-K), and collagen receptors were upregulated in the fibrosis-affected part. A literature search on the upregulated genes revealed several potential anti-fibrotic drugs.

CONCLUSION

Expression of genes involved in collagen metabolism in intestinal fibrosis affected terminal ileum of patients with CD reveals a plethora of drug targets. Inhibition of post-translational modification and altering collagen metabolism might attenuate fibrosis formation in the intestine in CD. Which compound has the highest potential depends on a combination anti-fibrotic efficacy and safety, especially since some of the enzymes play key roles in the physiology of collagen.

A review of the use of transient elastography in the assessment of fibrosis and steatosis in the post-liver transplant patient

Liver biopsy is considered the gold standard method for diagnosing and staging liver disease, particularly in the post-liver transplant setting. Given the invasive nature of biopsy, alternate means for accurately assessing liver fibrosis and steatosis are preferred especially as the number of patients with fatty liver disease is increasing. Transient elastography has been validated as a useful tool for evaluation of liver fibrosis, as has controlled attenuation parameter index as a tool for assessing steatosis. It is a non-invasive, rapid, and highly reproducible approach to demonstrate the presence of fibrosis among non-transplant patients with chronic liver disease of various etiologies. However, it has not yet found wide acceptance in liver transplant recipients. There are few published studies evaluating the merits and applicability of transient elastography to assess allografts after liver transplantation. We review the published data on the use of transient elastography with concurrent controlled attenuation parameter in liver transplant recipients and recommend its greater use to follow allograft function over time.

Tacrolimus (FK506) prevents early stages of ethanol induced hepatic fibrosis by targeting LARP6 dependent mechanism of collagen synthesis

Tacrolimus (FK506) is a widely used immunosuppressive drug. Its effects on hepatic fibrosis have been controversial and attributed to immunosuppression. We show that in vitro FK506, inhibited synthesis of type I collagen polypeptides, without affecting expression of collagen mRNAs. In vivo, administration of FK506 at a dose of 4 mg/kg completely prevented development of alcohol/carbon tetrachloride induced liver fibrosis in rats. Activation of hepatic stellate cells (HSCs) was absent in the FK506 treated livers and expression of collagen α2(I) mRNA was at normal levels. Collagen α1(I) mRNA was increased in the FK506 treated livers, but this mRNA was not translated into α1(I) polypeptide. No significant inflammation was associated with the fibrosis model used. FK506 binding protein 3 (FKBP3) is one of cellular proteins which binds FK506 with high affinity. We discovered that FKBP3 interacts with LARP6 and LARP6 is the major regulator of translation and stability of collagen mRNAs. In the presence of FK506 the interaction between FKBP3 and LARP6 is weakened and so is the pull down of collagen mRNAs with FKBP3. We postulate that FK506 inactivates FKBP3 and that lack of interaction of LARP6 and FKBP3 results in aberrant translation of collagen mRNAs and prevention of fibrosis. This is the first report of such activity of FK506 and may renew the interest in using this drug to alleviate hepatic fibrosis.

Potent antifibrotic activity of mTOR inhibitors sirolimus and everolimus but not of cyclosporine A and tacrolimus in experimental liver fibrosis

BACKGROUND & AIMS

Recurrence of chronic hepatitis C and progressive fibrosis in liver transplants is frequent and impairs both graft and patient survival. Whether or not the choice of immunosuppression affects progression of fibrosis remains unclear. The aim of the present study was to compare the potential of the commonly used immunosuppressants to halt experimental liver fibrosis progression.

METHODS

To induce liver fibrosis, rats underwent bile duct ligation and treatment with sirolimus (2mg/kg), everolimus (3mg/kg), tacrolimus (1mg/kg), and cyclosporin A (10mg/kg) daily for 5 weeks. Fibrosis, inflammation, and portal pressure were evaluated by histology, hydroxyproline levels, morphometry, hemodynamics, and hepatic gene expression.

RESULTS

Sirolimus and everolimus decreased fibrosis up to 70%, improved portal pressure, reduced ascites, and showed potent down-regulation of pro-fibrogenic genes, paralleled by a strong increase in matrix degradation (collagenase) activity; in contrast, tacrolimus and cyclosporine A had no or even aggravating effects on liver fibrosis in rats.

CONCLUSIONS

mTOR inhibition by sirolimus and everolimus in experimental liver fibrosis associates with significantly less fibrosis progression and portal hypertension than treatment with calcineurin inhibitors tacrolimus and cyclosporine A. These data suggest that the selection of the immunosuppressant could impact the recurrence of fibrosis in liver allografts.

Clinical outcome of HCV-related graft cirrhosis and prognostic value of hepatic venous pressure gradient

Hepatitis C virus (HCV) allograft cirrhosis may progress rapidly requiring re-transplantation but its course is little studied. We evaluated serially biopsied patients who developed HCV-related allograft cirrhosis. We assessed outcome of graft cirrhosis in 55 out of 234 consecutive patients and predictors of decompensation and mortality, including hepatic venous pressure gradient (HVPG) in 38. Allograft cirrhosis (Ishak stage 6, 60%; stage 5, 40%) was diagnosed between 12 and 172 months (median, 52) from transplantation; subsequent follow up was 22 (1-78) months. Faster development (<or=48 months) was associated with tacrolimus and nonuse of azathioprine and prednisolone. Decompensation occurred in 22% with a probability of not developing decompensation reaching 60% at 5 years. Survival among compensated patients was 77% at 5 years, but fell rapidly after decompensation (12% at 1 year). Decompensation and mortality were independently associated with HVPG >or= 10 mmHg, Child-Pugh score >or= 7, and albumin levels <or= 32 g/dl but not with fibrosis stage 5 or 6, HCV genotype (1b, 34%) or immunosuppression used after diagnosis of cirrhosis. In conclusion, Ishak stage 5 and 6 HCV-related cirrhosis have similar prognosis after liver transplantation. An HVPG >or= 10 mmHg, in addition to liver dysfunction, gives independent prognostic information prior to decompensation, allowing early relisting before prognosis becomes extremely poor.

Liver transplantation for hepatitis C virus related liver disease

Liver transplantation is a useful treatment for end stage liver disease of all aetiologies but recurrent disease presents an ongoing challenge, particularly for hepatitis C virus (HCV) where recurrence is almost universal. Immunosuppression is needed for all patients after transplantation and should be tailored to the individual patient, with particular problems being noted for those with HCV. The longer term effects of immunosuppression, particularly renal failure and the adverse effects of certain treatments on the liver graft, have become more important as survival improves and results are studied for longer periods after transplantation.

Differential effects of the immunosuppressant FK-506 on human ?2(I) collagen gene expression and transforming growth factor ? signaling in normal and scleroderma fibroblasts

OBJECTIVE

To investigate the effects of FK-506 on the expression of the human alpha2(I) collagen gene and transforming growth factor beta (TGFbeta) signaling in normal and scleroderma fibroblasts.

METHODS

The expression levels of type I procollagen protein and alpha2(I) collagen messenger RNA (mRNA) were analyzed by immunoblotting and Northern blotting, respectively. The promoter activities of alpha2(I) collagen gene and 3TP-Lux were determined by transient transfection assay. Interaction between TGFbeta receptor type I and FK-506 binding protein 12 (FKBP12) was evaluated by immunoprecipitation.

RESULTS

FK-506 did not affect the basal expression of type I procollagen protein or alpha2(I) collagen mRNA, but it significantly reduced the TGFbeta1-induced expression of type I procollagen protein and alpha2(I) collagen mRNA in normal fibroblasts. The effect of FK-506 was regulated posttranscriptionally, but not transcriptionally. In scleroderma fibroblasts, FK-506 significantly reduced the expression of type I procollagen protein and alpha2(I) collagen mRNA through posttranscriptional regulation, but not transcriptional regulation. FK-506 increased the basal activity of the 3TP-Lux promoter, but it did not affect the TGFbeta1-induced promoter activity in normal fibroblasts. In contrast, FK-506 did not affect the basal or the TGFbeta1-induced 3TP-Lux promoter activity in scleroderma fibroblasts. Furthermore, FKBP12, which protects TGFbeta receptor type I from ligand-independent activation by TGFbeta receptor type II, constitutively dissociated from TGFbeta receptor type I in scleroderma fibroblasts.

CONCLUSION

FK-506 inhibits alpha2(I) collagen gene expression by reducing the stability of mRNA without exhibiting its activation effect on TGFbeta signaling in scleroderma fibroblasts.

Plasma TGF-beta1 as a risk factor for gingival overgrowth

BACKGROUND AND AIMS

Induction of the pro-fibrotic growth factor TGF-beta1 has been suggested as a possible mechanism through which immunosuppressant drugs may induce gingival overgrowth. This study aims to investigate plasma levels of TGF-beta1 and relate them to the development and severity of gingival overgrowth in immunosuppressed transplant patients.

MATERIALS AND METHODS

One hundred and thirty-two ciclosporin-treated and 13 tacrolimus-treated transplant patients and 24 drug-free control subjects underwent a full periodontal examination including a determination of the presence and severity of gingival overgrowth.

RESULTS

Plasma TGF-beta1 concentrations were determined by ELISA, and were found to be significantly elevated in samples from the transplant patients (mean=29.1 ng/ml) as compared with controls (mean=6.1 ng/ml, p<0.0001). There was no significant difference between the levels of plasma TGF-beta1 in the ciclosporin- and tacrolimus-treated patient groups.

CONCLUSIONS

Furthermore, concomitant treatment with calcium channel blockers did not influence the levels of plasma TGF-beta1 in the patients group. The relationship between gingival overgrowth, independent periodontal variables and TGF-beta1 plasma concentrations was examined using univariate and multivariate regression analyses; low TGF-beta1 plasma concentrations were found to be a risk factor for gingival overgrowth in immunosuppressed patients concomitantly receiving a calcium channel blocker.

Impact of immunosuppression on immunopathogenesis of liver damage in hepatitis C virus-infected recipients following liver transplantation

1. Hepatitis C virus (HCV) infection in the allograft occurs in the setting of greater viral burdens than in patients pretransplantation. 2. Viral burden is increased by such immunosuppressive therapies as corticosteroids and interleukin-2 receptor antibodies. 3. Cholestatic HCV infection occurs in the setting of very high viral load and is almost certainly induced by overimmunosuppression. It is managed best by rapid reduction in levels of immunosuppression. 4. The more common chronic hepatitic HCV disease seems to behave at the molecular/cellular level in a fashion similar to the nontransplantation setting with activation of T helper subtype 1 inflammatory, profibrotic, and proapoptotic pathways. The role of immunosuppression in the acceleration of this disease is unclear, and rapid reduction in immunosuppressive doses may be detrimental. 5. Changes to definitions of types of HCV disease recurrence, disease severity, and acute allograft rejection in the presence of HCV infection are required to improve understanding of the pathogenesis.

Hepatobiliary diseases after kidney transplantation unrelated to classic hepatitis virus

Multiple studies during the past decades have identified chronic liver disease as an important cause of morbidity and mortality in kidney transplant recipients. It has been reported that up to 25% of patients will have some degree of abnormal liver functions during the immediate posttransplant period. In these patients, liver failure has been implicated as the cause of death in approximately 30% of the long-term survivors. While infections from hepatitis virus remain the main cause of ongoing liver damage, many other opportunistic infections with various potential to alter liver function have also been identified. In addition, posttransplant patients are also exposed to hepatotoxic adverse effects of many pharmacotherapeutics including immunosuppressive and nonimmunosuppressive agents. Since there are numerous reports dealing with classic viral hepatitis after kidney transplantation, this review primarily focuses on post-kidney transplant liver diseases which are not due to classic hepatitis viruses.

Antidiabetic thiazolidinediones inhibit collagen synthesis and hepatic stellate cell activation in vivo and in vitro

BACKGROUND & AIMS

The ligand-dependent transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma) is expressed in hepatic stellate cells (HSC), and its transcriptional activity is reduced during cell transdifferentiation in culture. PPARgamma transcriptional activation decreases platelet-derived growth factor-induced proliferation and inhibits alpha-smooth muscle actin expression in cultured HSC. The aim of our study was to evaluate whether oral administration of synthetic PPARgamma ligands, thiazolidinediones (TZD), might affect collagen deposition in animal models of liver fibrosis.

METHODS

The effect of 2 TZD (pioglitazone or rosiglitazone) was tested on liver fibrosis induced in rats by either toxin administration (dimethylnitrosamine or carbon tetrachloride) or bile duct ligation. In vivo PPARgamma activation was evaluated by gel shift assay using nuclear extracts from HSC isolated from control and treated rats.

RESULTS

Oral administration of TZD reduced extracellular matrix deposition and HSC activation in both toxic and cholestatic models of liver fibrosis. PPARgamma-specific DNA binding was significantly impaired in nuclear extracts of HSC isolated from fibrotic rats compared with HSC from control rats. TZD administration restored PPARgamma DNA binding in HSC nuclei. In vitro, TZD-induced PPARgamma activation inhibited collagen and fibronectin synthesis induced by transforming growth factor (TGF)-beta1 in human HSC, as measured by enzyme-linked immunosorbent assay and Northen blotting. TZD also reduced the TGF-beta1-induced activity of a 3.5-kilobase procollagen type I promoter transfected in human HSC.

CONCLUSIONS

These findings indicate that PPARgamma activation in HSC retards fibrosis in vivo and suggest the use of TZD for the treatment of liver fibrosis.

Rapamycin inhibits hepatic stellate cell proliferation in vitro and limits fibrogenesis in an in vivo model of liver fibrosis

BACKGROUND & AIMS

The accelerated course of hepatic fibrosis that occurs in some patients after liver transplantation is a major clinical problem. This response may be caused by the antirejection therapeutics, and in an earlier report we showed that FK-506 enhanced the fibrogenic process in in vivo and in vitro models of liver fibrosis. In the present study, the aim was to determine whether a new immunosuppressive agent, rapamycin, enhances or inhibits liver fibrosis.

METHODS

Effects of rapamycin were investigated in a carbon tetrachloride model of hepatic fibrosis in rats and on hepatic stellate proliferation in vitro.

RESULTS

Rapamycin inhibited extracellular matrix deposition in the rat model of fibrogenesis as determined by histological analysis, collagen content, messenger RNA levels of procollagen and transforming growth factor beta1, and tissue transglutaminase activity. Moreover, rapamycin decreased platelet growth factor-induced proliferation of hepatic stellate cells.

CONCLUSIONS

These findings indicate that the new antirejection agent rapamycin inhibits hepatic fibrosis and thus may become a valuable addition to the immunosuppression armamentarium.

Tacrolimus induces increased expression of transforming growth factor-beta1 in mammalian lymphoid as well as nonlymphoid cells

BACKGROUND

We and others have reported that cyclosporine (CsA) induces increased expression of transforming growth factor-beta1 (TGF-beta1) in vitro as well as in vivo. In view of similarities between tacrolimus and CsA with respect to immunosuppressive mechanisms, we determined whether tacrolimus, in a fashion similar to CsA, induces TGF-beta1 hyperexpression in mammalian cells.

METHODS

We studied the induction of TGF-beta1 mRNA by tacrolimus using reverse transcription-polymerase chain reaction and Northern blot analysis in normal human T cells and A-549 cells (human lung adenocarcinoma cell line), a cell line used to study the biology of TGF-beta and the induction of TGF-beta1 by CsA. We also measured the induction of TGF-beta1 protein by tacrolimus in activated human T cells, peripheral blood mononuclear cells, and A-549 cells, using sandwich enzyme-linked immunosorbent assay.

RESULTS

A significant increase in the TGF-beta1 mRNA expression was observed after treatment of T cells or A-549 cells. Tacrolimus treatment resulted also in heightened production of TGF-beta1 protein by activated T cells, A-549 cells, or peripheral blood mononuclear cells activated with anti-CD3, phytohemagglutinin, and concanavalin A.

CONCLUSIONS

Our observations that tacrolimus stimulates TGF-beta1 hyperexpression in mammalian cells suggest a unifying mechanism for the immunosuppressive as well as nephrotoxic properties of tacrolimus, as the multifunctional TGF-beta1 is a potent immunosuppressive and fibrogenic cytokine.

Drug therapy in the management of type 1 autoimmune hepatitis

Prednisone alone or in combination with azathioprine is the treatment of choice for severe type 1 autoimmune hepatitis. The combination regimen is preferred, especially in the elderly, because of a lower incidence of corticosteroid-related complications. Only patients with sustained severe laboratory abnormalities, bridging necrosis or multilobular necrosis on histological assessment, and/or incapacitating symptoms, have absolute indications for treatment based on controlled clinical trials. The institution of therapy must be individualised in other patients, based mainly on symptoms and disease behaviour. Serum aspartate aminotransferase and gamma-globulin levels are the most useful indices to monitor during therapy. Liver tissue examination is the best method of evaluating completeness of response. Most patients enter remission, but relapse occurs in 50 to 86% after drug withdrawal. Maintenance therapy with low dosages of prednisone or azathioprine can be used long term in patients who have relapsed repeatedly. Inability to achieve remission after 3 years (incomplete response), deterioration during therapy (treatment failure) and drug toxicity are unsatisfactory responses that warrant alternative strategies. Liver transplantation is effective in managing decompensated disease, but recurrence of autoimmune hepatitis after transplantation is possible. Tacrolimus and budesonide are promising new drugs.

Effects of ethanol on gene expression in rat bone: transient dose-dependent changes in mRNA levels for matrix proteins, skeletal growth factors, and cytokines are followed by reductions in bone formation

Several studies were performed in female rats to determine dose and time course changes in mRNA levels for matrix proteins in bone after a single administration of ethanol. As expected, dose-dependent transient increases in blood ethanol were measured. Additionally, there was mild hypocalcemia with no change in immunoreactive parathyroid hormone. Coordinated dose-dependent increases in mRNA for type 1 collagen, osteonectin, and osteocalcin were noted in the proximal tibial metaphysis 6 hr after ethanol was given, with the peak values occurring at a dose of 1.2 g/kg (0.4 ml). Similar increases in mRNA levels for matrix proteins were noted in lumbar vertebrae after ethanol treatment. The changes were specific for bone; ethanol had no effect on mRNA levels for matrix proteins in the uterus or liver, although the mRNA concentrations tended to be reduced in uterus. Message levels for several cytokines implicated in the regulation of bone turnover were also assayed; mRNA levels for transforming growth factor-beta1, transforming growth factor-beta2, interferon-gamma, and interleukin-6 were unchanged at doses ranging from 0.14 to 1.7 g/kg. At the highest dose of ethanol, the mRNA level for tumor necrosis factor-alpha was elevated while the level for insulin-like growth factor-1 was reduced. The time course effects of ethanol (0.4 ml dose) were determined in a separate experiment. Ethanol resulted in a transient increase in mRNA levels for the three bone matrix proteins assayed. However, matrix protein synthesis, as determined by incorporation of 3H-proline into the proximal tibial metaphysis, was not changed after 6 hr. The changes in mRNA levels for the matrix proteins were preceded by brief, transient decreases in mRNA levels for interleukin-1beta, interferon-gamma, and migration inhibitory factor, and followed by a more prolonged decrease in the mRNA level for insulin-like growth factor-1. A subsequent study was performed to determine the effects of repetitive daily treatment with ethanol on rat bone. After 7 days, there were highly significant decreases in the mRNA level for type 1 collagen, as well as decreased bone formation. These results suggest that ethanol may alter bone metabolism by disturbing signal transduction pathways that regulate the expression of genes for bone matrix proteins, skeletal growth factors, and cytokines.

Transforming growth factor-beta1 in plasma and liver of children with liver disease

Although several liver diseases of childhood, particularly biliary atresia (BA) and cystic fibrosis (CF) liver disease (CFLD) are characterized by hepatic fibrosis, the pathogenesis of this process is incompletely understood. The cytokine transforming growth factor-beta1 (TGF-beta1) has been implicated in hepatic fibrosis in experimental animals, in which both the hepatic expression and plasma concentration of this cytokine are increased. The objective of our study was to determine whether there are similar alterations of TGF-beta1 in patients with hepatic fibrosis secondary to either BA and/or CFLD. The study design was as follows. In study 1, plasma TGF-beta1 was assessed by ELISA in 9 children with BA undergoing liver transplantation, 11 patients with CFLD, and appropriate control subjects. In study 2, hepatic expression of TGF-beta1 protein (assessed immunohistochemically) and hepatic fibrosis were scored semiquantitatively, on a 1-3 scale, by blinded investigators, in archival liver biopsy specimens from 10 children with BA, 10 with CFLD, and from 10 older children with normal hepatic histology, as well as in 4 patients with liver diseases of various etiologies. Simultaneous plasma and liver TGF-beta1 studies were performed in 8 patients with liver disease. Results were as follows. Plasma TGF-beta1 values were inversely correlated with age in healthy subjects (r=-0.54, p < 0.0001). The plasma TGF-beta1 protein of children with BA was decreased (13+/-2 ng/mL) compared with values for healthy children (42+/-6 ng/mL, n=10, p < 0.005). Similarly, the plasma TGF-beta1 concentration in patients with CFLD was also decreased compared with values for children with CF and normal serum liver profiles (n=14) (2+/-1 ng/mL versus 12+/-1, p < 0.05). However, the plasma TGF-beta1 concentration was increased in two patients with other types of liver disease. The hepatic expression of TGF-beta1 was increased in the presence of hepatic fibrosis in all types of liver diseases studied. Forty-six percent of patients had both marked hepatic fibrosis and marked TGF-beta1 labeling; 86% of samples without fibrosis showed no TGF-beta1 labeling, p=0.007. In conclusion, these studies have established the association of hepatic TGF-beta1 protein and hepatic fibrosis in several common liver diseases of childhood. Our data also suggest that, in children, plasma TGF-beta1 does not appear to be a useful marker of hepatic expression of this cytokine.

Cholestasis and alterations of glutathione metabolism induced by tacrolimus (FK506) in the rat

BACKGROUND

Tacrolimus (FK506) is an immunosuppressive agent used for the prevention of allograft rejection after organ transplantation. The aim of this study was to investigate the effects of chronic tacrolimus treatment on bile secretion in rats.

METHODS

Tacrolimus was administered intraperitoneally at doses of 0.2, 0.5, and 0.8 mg/kg/day for 6 weeks.

RESULTS

Bile flow was significantly reduced at doses of 0.5 mg/kg and 0.8 mg/kg (-25% and -32%, respectively). Bile acid secretion was not significantly modified, but bicarbonate secretion decreased at doses of 0.5 mg/kg and 0.8 mg/kg (-23% and -29%, respectively). Glutathione secretion was significantly reduced at doses of 0.5 mg/kg (-29%) and 0.8 mg/kg (-49%). Liver glutathione concentration was reduced at the higher dose (-17%). Liver gamma-glutamyl-cysteinyl synthetase activity was elevated (+22%, +10, and +15%) and gamma-glutamyl transpeptidase activity was reduced (-18%, -40%, and -25%) at all doses. Dichlorofluorescein and thiobarbituric acid-reactive substance concentrations were not significantly modified. Liver glutathione peroxidase activity increased at doses of 0.5 mg/kg (+65%) and 0.8 mg/kg (+56%). Kidney concentration of thiobarbituric acid-reactive substances was significantly increased at doses of 0.5 mg/kg (+17%) and 0.8 mg/kg (+12%).

CONCLUSIONS

Our data indicate that tacrolimus at high doses induces cholestasis by inhibiting primarily biliary excretion of glutathione and, to a lesser extent, bicarbonate. The decrease in biliary glutathione secretion is not due to a lower synthesis or degradation and could be related to its increased sinusoidal efflux.

Tacrolimus impairs wound healing: a possible role of decreased nitric oxide synthesis

BACKGROUND

The effect of the immunosuppressant tacrolimus on wound healing is not known. Tacrolimus has been shown to decrease nitric oxide synthesis. The systemic inhibition of wound nitric oxide synthesis leads to impaired healing.

METHODS

We studied the effect of systemic tacrolimus treatment on wound-breaking strength and collagen deposition 10 days after wounding in rats and to correlate the outcome of healing with wound nitric oxide synthesis. Beginning at the day of wounding, rats were treated once daily by intraperitoneal injections with 0.5, 1.0, or 2.0 mg tacrolimus/kg body weight. Nitrite and nitrate were measured in wound fluid as an index of wound nitric oxide synthesis. Expression of inducible nitric oxide synthase in the wound was investigated by immunohistochemistry. Splenic lymphocytes were tested for proliferative activity. Tacrolimus levels in blood and wound fluid were measured by enzyme-linked immunosorbent assay.

RESULTS

Systemic tacrolimus treatment was well tolerated by all rats. Tacrolimus accumulated in wound fluid. Tacrolimus levels in wound fluid were found to be approximately 10-fold higher than blood levels (P < 0.001). Tacrolimus (2.0 mg/kg/day) reduced wound-breaking strength (P < 0.01) and collagen deposition (P < 0.05). This was paralleled by decreased wound nitrite + nitrate levels (P < 0.001) and wound-inducible nitric oxide synthase expression. Splenic lymphocyte proliferative activity was significantly decreased by 1.0 and 2.0 mg tacrolimus/kg body weight/day (P < 0.05), indicating that the tacrolimus doses used were immunosuppressive.

CONCLUSION

Our data show for the first time that tacrolimus impairs wound healing, and this is reflected by diminished wound nitric oxide synthesis.

Mechanism of fibrosis in experimental tacrolimus nephrotoxicity

The clinical use of tacrolimus (FK506) is limited by nephrotoxicity. The pathogenesis of fibrosis in chronic FK506 nephrotoxicity remains unknown. Because transforming growth factor (TGF)-beta plays a key role in the fibrogenesis of many diseases, including cyclosporine nephrotoxicity, we studied a salt-depleted rat model of chronic FK506 nephropathy in which clinically relevant FK506 blood levels are obtained and which shows similarities to the lesions described in patients receiving FK506. Pair-fed rats were treated with either FK506 (1 mg/kg/day s.c.) or an equivalent dose of vehicle and were killed at 7 or 28 days. Characteristic histologic changes of tubular injury, interstitial fibrosis, and arteriolopathy developed in FK506-treated rats at 28 days and were accompanied by worsening kidney function, decreased concentrating ability, and enzymuria. FK506-treated kidneys had a progressive increase in the expression of TGF-beta1 and matrix proteins (biglycan, tenascin, fibronectin, and type I collagen). This effect seems to be specific because the expression of type IV collagen, a basement membrane collagen, was not affected. Matrix deposition was present mostly in the tubulointerstitium and vessels in accordance with the FK506 chronic lesion. The expression of plasminogen activator inhibitor-1, a protease inhibitor influenced by TGF-beta, followed TGF-beta1 and matrix proteins, suggesting that the fibrosis of chronic FK506 nephropathy likely involves the dual action of TGF-beta1 on matrix deposition and degradation. Since both peripheral and tissue renin expression were elevated with FK506, the renin-angiotensin system may play a role in the pathogenesis of this condition.